1. Field of the Invention
The present invention relates to a device for fusing and fixing a transferred toner of a predetermined image onto a print paper. More particularly, the present invention relates to a fusing device which can instantly control induced current supplied to a fusing unit in an image printing apparatus which heats the fusing unit using the induced current.
2. Description of the Related Art
A conventional image printing apparatus includes a fusing device which applies predetermined pressure and heat to a print toner to fuse and fix a transferred toner of a predetermined image onto a print paper. The fusing device includes a fusing unit to apply a predetermined heat to the print toner, and a pressure unit to apply a predetermined pressure to the print toner. The fusing unit includes a heating element which generates heat to fuse and fix the toner onto the print paper, and a fusing roller which receives the heat produced by the heating element and transfers the heat to the print paper.
FIG. 1 is a schematic horizontal cross-section view of a fusing unit 10 of a fusing device using a halogen lamp as a heat source. Referring to FIG. 1, the fusing unit 10 includes a fusing roller 11 and a heating element 12 composed of the halogen lamp installed in the center of the heating element 12. A coating layer 11a made of Teflon is formed on the surface of the fusing roller 11. The heating element 12 generates heat inside the fusing roller 11, and the fusing roller 11 is heated via the radiant heat emitted from the heating element 12.
FIG. 2 is a block diagram of a conventional fusing device using a halogen lamp as a heat source. Noise signals included in a voltage applied from a predetermined power voltage 210 are filtered via a line filter unit 220, and the filtered input voltage is supplied to a heating unit 250 of a fusing roller 240. The heating unit 250 is resistance heated by the input voltage, and the heat generated at the heating unit 250 heats the fusing roller 240. The temperature of the fusing roller 240 is sensed by a sensing unit 260, and a controlling unit 270 controls the on/off operation of a switch 230 to control the temperature of the fusing roller 240 based on the temperature of the fusing roller 240.
A conventional fusing unit using a halogen lamp as a heat source requires several seconds to several minutes of warm-up time to heat a fusing roller from when power is supplied to the fusing unit until it reaches a target fusing temperature. Therefore, a user has to wait during the long warm-up time.
When using the halogen lamp as the heat source, the current flowing through the heating unit is determined by the applied voltage, and the current which flows to the heating unit drastically increases when the voltage is applied, thereby reducing the flicker characteristics of the fusing device.